Date of Award

1-1-2019

Language

English

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

College/School/Department

Department of Nanoscale Science and Engineering

Program

Nanoscale Sciences

Content Description

1 online resource (xiv, 204 pages) : color illustrations.

Dissertation/Thesis Chair

Ji Ung Lee

Committee Members

Cory D. Cress, Spyros Gallis, Carl Ventrice, Vincent LaBella

Keywords

2D materials, Graphene, p-n junction, Quantum Hall Effect, Radiation Effects, Schottky-Mott, Nanotubes, Electron transport, Carbon, Semiconductor doping, Semiconductors, Heterostructures

Subject Categories

Condensed Matter Physics | Nanoscience and Nanotechnology | Quantum Physics

Abstract

This dissertation presents theoretical and experimental studies in carbon nanotubes (CNTs), graphene, and van der Waals heterostructures. The first half of the dissertation focuses on cutting edge tight-binding-based quantum transport models which are used to study proton irradiation-induced single-event effects in carbon nanotubes [1], total ionizing dose effects in graphene [2], quantum hall effect in graded graphene p-n junctions [3], and ballistic electron focusing in graphene p-n junctions [4]. In each study, tight-binding models are developed, with heavy emphasis on tying to experimental data. Once benchmarked against experiment, properties of each system which are difficult to access in the laboratory, such as local density of states, local current density, and quantum transmission probability, are extracted to build our physical intuition. The second half of the dissertation covers experimental work on transport in van der Waals heterostructures. High-quality samples, evidenced by measurements of quasi-ballistic graphene p-n junctions, are enabled by encapsulation in hexagonal boron nitride, assembled using a modified dry transfer technique. The Schottky-Mott limit, previously only a textbook example, is probed in gated graphene-WSe2 heterojunctions [5]. Schottky barrier measurements as a function of gate voltage reveal perfect barrier tuning, following the Schottky-Mott rule. Enabled by the lack of Fermi-level pinning at the graphene-WSe2 interface, a method for dynamically tuning the Schottky diode ideality factor is demonstrated. Finally, an analytical model describing tuning of the junction is developed.

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